Ambient Air Monitoring of Methyl Bromide

GOOD PRACTICE GUIDE FOR AMBIENT AIR MONITORING OF METHYL BROMIDE AT FUMIGATION SITES IN NEW ZEALAND

Final

13 December 2012

The SKM logo trade mark is a registered trade mark of Sinclair Knight Merz Pty Ltd.

Ambient Air Monitoring of Methyl Bromide

GOOD PRACTICE GUIDE FOR AMBIENT AIR MONITORING OF METHYL BROMIDE AT FUMIGATION SITES IN NEW ZEALAND

Final

13 December 2012

Sinclair Knight Merz Level 3, 86 Customhouse Quay, PO Box 10-283 Wellington, New Zealand Tel: +64 4 473 4265 Fax: +64 4 473 3369 Web: www.globalskm.com

COPYRIGHT: The concepts and information contained in this document are the property of Sinclair Knight Merz Limited. Use or copying of this document in whole or in part without the written permission of Sinclair Knight Merz constitutes an infringement of copyright.

LIMITATION: This report has been prepared on behalf of and for the exclusive use of Sinclair Knight Merz Limited’s Client, and is subject to and issued in connection with the provisions of the agreement between Sinclair Knight Merz and its Client. Sinclair Knight Merz accepts no liability or responsibility whatsoever for or in respect of any use of or reliance upon this report by any third party.

SINCLAIR KNIGHT MERZ

PAGE i

Contents

1. Introduction 3

1.1 Purpose of the Good Practice Guide 3

1.1. Scope 3

1.2. Target Audience 4

1.3. Good Practice 4

1.4. Stakeholders in Methyl Bromide Reduction (STIMBR) 4

2. Fumigation Activities and Legislative Considerations 6

2.1. Fumigation Activities 6

2.2. Legislative Considerations 6

3. Ambient Air Monitoring Method Selection 9

3.1. Introduction 9

3.2. Photo-Ionisation Detectors (PIDs) 9

3.2.1. Applicability of PIDs 9

3.2.2. Limitations of PIDs 10

3.3. Gas Detection Tubes 11

3.3.1. Applicability of Gas Detection Tubes 11

3.3.2. Limitations of Gas Detection Tubes 11

3.4. Alternative Methods for On-Site Analysis of Methyl Bromide 12

3.4.1. Applicability 12

3.4.2. Limitations 12

3.5. Ambient Air Sampling Methods for Laboratory Analysis of Methyl Bromide 12

3.6. General Advice on Instrument Selection 13

4. Site Selection 15

4.1. Site Numbers and Selection 15

4.1.1. The effect of land use activities on monitoring 16

4.2. Geometric Considerations and Buffer Zones 17

4.3. Locations over Water 19

4.4. Topography (Geographic Location) 19

4.5. Climate and Meteorology 20

4.6. Site Selection Checklist 22

5. Sampling and Data Recording 25

5.1. Introduction 25

5.2. EPA Data Collection Requirements 25

5.3. Pre-Sampling 26

5.4. During Sampling 28

SINCLAIR KNIGHT MERZ

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5.5. Post-Sampling and Sample Handling 29

5.6. Further Information 32

5.6.1. Calibration 32

5.6.2. Data Logging 32

5.6.3. Quality assurance and quality control (QA/QC) 32

5.6.4. Instrument Use 33

6. Presentation of Results 35

6.1. Introduction 35

6.2. Meteorological Data 35

6.3. Results of Monitoring 36

6.4. Calculation of Time-Averaged Methyl Bromide Concentrations 39

6.4.1. Calculating 1-hour and 24-hour Averages 39

6.4.2. Calculating Annual Averages 40

6.4.3. Reporting Averages 42

6.5. Conclusion of Results 42

7. References 43

Appendix A Ambient Monitoring Field Data Sheets 44

Appendix B Case Study: Monitoring Method 54

SINCLAIR KNIGHT MERZ

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Glossary

Buffer Zone The area around a fumigation outside of which the Tolerable Exposure Limits

(TELs) must not be exceeded.

Dispersion The transport and mixing of contaminants to the atmosphere from their source.

ERMA Environmental Risk Management Authority (now incorporated into the

Environmental Protection Authority)

ERMA

Decision

The ERMA Decision regarding the Application for the Reassessment of a

Hazardous Substance under Section 63 of the Hazardous Substance and New

Organisms ACT 1996. Name of substances: Methyl Bromide and formulated

substances containing methyl bromide. Application Number: HRC08002 28

October 2010

EPA Environmental Protection Authority

Exceedence When the monitored concentration of methyl bromide in air at a specific location

averaged over 1 hour, 24 hours or 1 year exceeds the relevant TEL.

GPG Good Practice Guide

HSNO Hazardous Substances and New Organisms Act 1996

IANZ International Accreditation New Zealand

mg/m3

Milligrams per cubic metre. This is the unit used to express the measured

concentration of methyl bromide in air as a mass to volume ratio.

PID Photo Ionization Detector. A device that measures the concentration of volatile

organic compounds by ionizing molecules using high energy UV light.

ppmv Parts per million by volume (1 ppmv of methyl bromide is equal to

approximately 3.9 mg/m3of methyl bromide in ambient air).

Recapture

Technology

A system for capturing methyl bromide following a fumigation event so that the

release of methyl bromide into the environment is minimized.

Sensitive

Receptor

People or institutions with people that are particularly susceptible to effects from

environmental pollution, such as the elderly, very young children, people already

weakened by illness or condition such as asthma, and persons engaged in

strenuous exercise.

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Glossary

TELs Tolerable Exposure Limits are the time based (1 hour, 24 hour or 1 year) average

concentrations of methyl bromide that are not to be exceeded beyond the buffer

zone.

WES-TWA Workplace Exposure Standard – Time Weighted Average

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1. Introduction

1.1 Purpose of the Good Practice Guide

The purpose of this Good Practice Guide (GPG) is to provide guidance to fumigators, monitoring

technicians and port authorities concerning ambient air monitoring for methyl bromide during

fumigation venting in New Zealand.

This GPG has been prepared to assist in compliance with the monitoring controls set out in the

Environmental Risk Management Authority (ERMA) Decision1 (the Decision) for reassessment of

methyl bromide and the continued systematic and robust collection of valid data on methyl bromide

concentrations in air at the landward security/property boundary or buffer zone of the site under

investigation during fumigation venting.

1.1. Scope

This GPG has been prepared to provide a standard for the measurement of methyl bromide

concentrations in the air and the management of monitoring data. The GPG has been designed to

ensure that monitoring data and management is carried out:

Correctly - air quality monitoring is of a high quality and free from errors (measurement

precision and accuracy);

Consistently - data is correctly recorded, analyzed, processed, reported and archived following

good monitoring practice principles;

Efficiently - suppliers and users of methyl bromide ambient air quality data have easy and

rapid access to methods, procedures and new developments; and

Cost effectively – appropriate information is obtained at the least cost.

The GPG describes:

Typical methyl bromide fumigation activities and sites where fumigations are undertaken;

Methyl bromide ambient air monitoring methods and equipment;

The criteria to consider for the selection of appropriate ambient air monitoring locations at the

boundary of a site or buffer zone where the methyl bromide fumigation is being carried out;

1 Environmental Risk Management Authority Decision

Application for the Reassessment of a Hazardous Substance under Section 63 of the Hazardous Substance and New Organisms ACT 1996 Name of substances: Methyl Bromide and formulated substances containing methyl bromide. Application Number: HRC08002 28 October 2010

PAGE 4

Monitoring techniques to be followed including calibration of equipment, sampling data to be

recorded, sampling periods, QA/QC checks; and

How the data collected from the monitoring of a methyl bromide fumigation should be

reported.

This GPG is intended for use whenever methyl bromide is being used without recapture technology

including but not limited to ports, container yards and transportation terminals and excluding soil

fumigations. It is expected that at times of fumigant introduction and ventilation that buffer zones

as set out in the ERMA Decision will be in place and of appropriate scale to prevent public access

and shall meet the conditions set out in the Decision. This GPG is designed to provide guidance on

monitoring the concentration of fumigant at the landward boundary of the buffer zone rather than

within it. While this GPG addresses multiple methods to achieve compliant monitoring it is focused

on monitoring using non-methyl bromide-specific real time sampling methods.

Specific methods recommended here are photo-ionization detectors (PIDs), particularly in

combination with methyl-bromide specific gas monitoring tubes.

Other methyl bromide-specific monitoring methods such as USEPA Compendium Methods TO-15

(TO-15) and TO-17 (TO-17) are also discussed, but it is understood that the expense of these

methods make them impractical for fumigation monitoring to meet the requirements of the

Decision.

This GPG is not intended for use in relation to fumigation cells or fumigant capture installations.

1.2. Target Audience

This GPG is intended for use by all parties responsible for the ambient air monitoring of methyl

bromide fumigation venting. This may include but is not limited to fumigators, health and safety

inspectors, compliance officers, port authorities, and environmental or air quality technicians.

1.3. Good Practice

This GPG is considered as “Good Practice” for ambient air monitoring of methyl bromide and may

require a higher level of performance than that required by the HSNO regulations and decisions. In

order to clarify what is mandatory the reader is referred to the Conditions set out in the ERMA

Decision.

1.4. Stakeholders in Methyl Bromide Reduction (STIMBR)

STIMBR is an incorporated society which brings together industry, government and research

organisations, and individuals with the aim of providing a united voice in support of initiatives

aimed at enhancing market access and biosecurity clearances for goods and products while

PAGE 5

reducing the release of methyl bromide into the atmosphere and seeking the long term reduction in

its use.

The group provides an interface between users of methyl bromide, fumigators applying treatments,

government departments concerned with reducing the use of ozone depleting substances,

researchers seeking alternative treatments and strategies, and other affected parties. This GPG was

commissioned by STIMBR in response to the ERMA Decision.

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2. Fumigation Activities and Legislative Considerations

2.1. Fumigation Activities

This GPG is intended to offer guidance for the monitoring of methyl bromide in ambient air during

methyl bromide fumigation activities in accordance with the ERMA decision. As such, the

guidance applies to the monitoring of ambient air concentrations of methyl bromide at the landward

boundary of buffer zones or controlled areas for any application of methyl bromide that does not

utilize recapture technology, excluding fumigation of soils. These applications include fumigation

of the following:

Shipping containers: fumigation of products of any type within closed shipping containers;

Tarpaulin enclosures: fumigation of products of any type enclosed within gas tight tarpaulins

or covers, sealed to hard sealed ground surface with tape, sandbags, water snakes or similar;

and,

Ships holds: fumigation of products of any type within closed holds of ships.

These three types of fumigation may differ from one another in size by an order of magnitude in

terms of mass of product and fumigant used. Total methyl bromide fumigant quantity per shipping

container is almost always less than 10 kg, while within a tarpaulin enclosure it may exceed 100 kg

of fumigant, and a ship‟s hold may require a tonne or more. These quantities vary not only with

the volume of the enclosure, but also with bio-security standards of the importing country, the

nature of the product being treated, and temperature. Fumigant concentrations commonly require a

methyl bromide concentration ranging between 46 to 120 grams per cubic metre, or roughly 12,000

to 30,000 parts per million over the gross volume of the enclosure.

2.2. Legislative Considerations

The relevant air quality guidelines and exposure limits for public exposure to methyl bromide at the

time of this report are discussed in this section. The ERMA decision set Tolerable Exposure Limits

(TELs) to prevent adverse effect to human health from methyl bromide during fumigations. These

TELs cannot be exceeded outside the buffer zone established around the fumigation activity. The

TELs were established for 1-hour, 24-hour and annual averaging periods, and are provided in

Table 1 below. The TELs are based on epidemiological and exposure studies undertaken by

toxicologists, and are designed to protect the most sensitive members of the population from

adverse effects from exposure to methyl bromide. No adverse effects on human health are

expected below these limits.

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Table 1 Tolerable Exposure Limits (TELs) for Methyl Bromide in Air

Averaging Period TEL Concentration

Parts per million (ppm) Milligrams per cubic metre (mg/m3)

TELair (annual) 0.0013 0.005

TELair (24 hour) 0.333 1.3

TELair (1 hour) 1 3.9

In addition to the TELs, the Department of Labour has set a Workplace Exposure Standard as a

time weighted average (WES-TWA) over an eight hour day to protect workers from excessive

exposure to methyl bromide. The WES-TWA for methyl bromide is 5 ppm (19 mg/m3) as an 8-

hour average2. This standard is applicable to workers within the fumigation and buffer zones of a

fumigation activity, but is not applicable to public exposure which is necessarily more stringent to

protect sensitive members of populations.

A conceptual illustration of a buffer zone around a fumigation event is shown in Figure 1, and

shows the Risk Area in which personal protective equipment for methyl bromide must be worn, a

buffer zone in which the WES-TWA for methyl bromide applies, and outside the buffer zone where

the TELs for air apply. This monitoring guide is designed to confirm that the TELs for methyl

bromide are not exceeded outside the boundary of the buffer zone during fumigation events.

2 Department of Labour, Workplace Exposure Standards and Biological Exposure Indices, September 2010.

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Figure 1 Illustration of Risk Area and Buffer Zones Around Fumigation Events3

3 EPA, Methyl Bromide Fumigations Post-reassessment guidance for fumigators, April 2011.

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3. Ambient Air Monitoring Method Selection

3.1. Introduction

A variety of methods are available for measuring contaminants in ambient air, with an equally wide

variation in cost and precision. Specific monitoring methods should be selected based on the

purpose, objectives and budget of the monitoring programme. This section discusses methods for

monitoring methyl bromide in ambient air and provides details concerning methodologies

historically used for the monitoring of methyl bromide fumigations in New Zealand. Each

subsection provides an overview of the methodology, advice on where and when this method is

applicable for use, and the limitations associated with each method. Descriptions of methyl

bromide monitoring equipment are presented here as examples only and do not limit monitoring

staff to the use of this equipment. Alternative methods not mentioned here may exist or be

developed over time, and may be used assuming they meet minimum requirements of instrument

sensitivity and response time. Choosing the appropriate monitoring equipment is critical for

achieving the aims of the monitoring program.

3.2. Photo-Ionisation Detectors (PIDs)

Photo-ionisation Detectors (PIDs) are the most commonly used instruments for monitoring methyl

bromide during fumigation events in New Zealand. PIDs are used to measure concentration of

volatile organic compounds (VOCs), using an ultra violet lamp producing high energy photons to

break down gas molecules into positively charged ions. The electrical current produced in the

reaction becomes the signal output for the unit, providing a direct reading of concentration in near

real-time.

3.2.1. Applicability of PIDs

PIDs can be used to directly detect a wide range of VOCs, including methyl bromide. PIDs are not

specific to any one compound, and so have limited application in environments where there may be

a mixture of VOCs4. However, the relatively low cost and ease of use make them a preferred

option for screening monitoring. The primary advantages of using PIDs for monitoring methyl

bromide include:

Relatively low cost;

Robust for field use;

Direct reading and quick response time;

4 VOCs commonly found in air include: paints, solvents, fuels, components in exhaust fumes and timber

preservatives.

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Small size for portability and ease of handling; and

Simplicity of operation.

PIDs are the most readily available and commonly used instruments for monitoring methyl

bromide in ambient air for these reasons. PIDs are typically calibrated with an isobutylene

calibration gas, and have experimentally determined response factors for other compounds. For

example, a typical response factor for methyl bromide relative to isobutylene is 1.7, meaning a

reading of 1 ppm on a PID calibrated to isobutylene would equate to 1.7 ppm of methyl bromide

(assuming the response is due solely to methyl bromide and there is no interference from other

VOCs).

PIDs must be calibrated no more than 3 months prior to use, and must be checked using zero and

span gases before and after the sampling event. Hydrocarbon-free air should be used as the zero

gas. 21% oxygen in nitrogen is commonly used but may be difficult to obtain, therefore ambient

air passed through a charcoal scrubber can be used and is recommended. Isobutylene is commonly

used as the span gas (a premixed cylinder of isobutylene in nitrogen). The span gas should be at

80% of the full scale of the PID measurement range, and ideally the range should encompass the

expected concentrations.

3.2.2. Limitations of PIDs

Limitations of using PIDs for methyl bromide monitoring include:

Instrument response is not specific to methyl bromide - other VOCs in the air may influence

readings

Limited range of detection ( a typical lower detection limit for PIDs is 0.1 ppm); and,

Sensitivity to moisture.

Despite the ease of use of PIDs, the primary drawback is that they are not specific to methyl

bromide, and so a positive reading is not necessarily an indication that methyl bromide is present.

This is particularly relevant when monitoring in an area where there are other potential sources of

VOCs which could be detected by the instrument. For this reason, a positive reading by a PID

should be confirmed with a methyl bromide-specific analysis, such as gas detection tubes.

Alternatively a grab sample can be taken with a canister or extracted through an adsorbtion

cartridge to be analysed by GC or GC-MS at an off-site laboratory.

PIDs are also sensitive to moisture in the monitoring environment. Condensation of moisture on

the lamp can be a cause of instrument drift and may result in a false positive reading. On the other

hand, inlet filters designed to remove precipitation from the gas stream can accumulate water

droplets and partially scrub out methyl bromide from the sample, resulting in lower concentrations.

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Any methyl bromide monitoring conducted using PIDs should be carried out in conjunction with

methyl bromide-specific gas detection tubes to verify that a positive reading is not due to

instrument drift, moisture interference, or detection of other VOCs. When using gas detection

tubes or a grab sample for verification of a positive PID reading, the sample must be taken at the

same location and the same time in which the PID shows a positive reading.

3.3. Gas Detection Tubes

Gas detection tubes are thin glass tubes with calibration scales printed on them to enable direct

reading of concentrations of the substance being measured. Each tube contains a matrix (e.g. silica

gel, alumina) which binds selected detection reagents that are sensitive to the target substance in

order to produce a distinct layer of color change. The tubes are hermetically sealed at both ends.

After snapping off the sealed ends, a known volume of sample air is drawn through the detector

tube manually by a hand-held pump.

3.3.1. Applicability of Gas Detection Tubes

In the context of monitoring methyl bromide fumigation events, gas detection tubes are primarily

used for spot-checking instrument readings of PIDs. The applicability of using methyl bromide-

specific gas detection tubes include:

On-site measurements can be performed easily at any time and place, and within a short time;

Easy-to-check direct reading;

Extensive measuring range (based on tube type and sample volume);

No calibration required; and

Long shelf-life with excellent long-term stability if appropriately stored.

The simplicity of this method makes it easy to use and does not require a highly trained operator.

The easy-to-check readings reduce potential operator error and can give quick and accurate results.

Detection ranges can be easily adjusted by selecting different tube types and by altering air

volumes sampled. The tubes are pre-calibrated and do not require complicated calibration

procedures required for other methods. Methyl bromide-specific tubes have an accuracy of 10% for

measurements of 0.1 to 0.4 parts per million (ppm).

3.3.2. Limitations of Gas Detection Tubes

The main disadvantage of gas detection tubes is that they only provide a snapshot analysis at one

location for the time that the sample is drawn (typically less than a few minutes), and so are not

applicable for the continuous monitoring required for methyl bromide fumigations. In theory a

series of tubes could be drawn by a monitoring technician throughout the course of a fumigation

PAGE 12

ventilation. However, the expense and resource demand make them unrealistic for these

monitoring purposes on their own.

3.4. Alternative Methods for On-Site Analysis of Methyl Bromide

There are a variety of analytical methods capable of measuring methyl bromide in real time at

ambient-air concentrations. In addition to monitoring methyl bromide specifically, these methods

generally have a much greater sensitivity and can detect lower concentrations compared to PIDs.

However these methods require a significant cost for purchase or rental of equipment relative to

PIDs, and also require a much higher level of operator training. The analytical methods currently

in use include:

Electrochemical sensors;

Gas Chromatography (GC);

Gas Chromatography-Mass Spectrometry (GC-MS); and,

Fourier Transform Infrared spectroscopy (FTIR);

3.4.1. Applicability

Specificity to methyl bromide;

Are accurate down to ppb levels;

Real-time logged data easily downloaded and interrogated; and

GC, GC-MS and FTIR are capable of measuring a wide range of VOCs other than methyl

bromide.

3.4.2. Limitations

Significantly greater cost in instrument purchase, maintenance and consumables;

The instruments are less portable than other methods; and,

The instruments are significantly more complex and require a higher degree of operator

training.

The specificity of these analytical methods to methyl bromide, together with their lower detection

limit, makes them an attractive alternative to PIDs. However the large initial capital outlay, cost of

maintenance and operation, and training of operators in the use of the instrumentation make them

unlikely alternatives to using PIDs for fumigation monitoring at this time.

3.5. Ambient Air Sampling Methods for Laboratory Analysis of Methyl Bromide

These methods entail collection of a sample of ambient air in the field followed by laboratory

analysis by GC, GC-ECD or GC-MS. Typically, a known volume of air is pumped through a

PAGE 13

sorbent trap5, or a whole-air sample is collected in a Tedlar bag

6 (or equivalent) or evacuated steel

canister over a known period of time. The usefulness of this method is that the sampling

techniques are relatively simple, and it is not necessary to purchase the analytical equipment.

Using an International Accreditation New Zealand (IANZ) certified laboratory for sample analysis

provides some guarantee of data quality. A primary disadvantage of these methods is that they

entail a significant delay between the collection of the sample and the obtaining of results.

Furthermore the expense of the analysis would limit the number of samples during fumigation, and

is therefore not appropriate for the high time-resolved measurements that fumigation requires (i.e.,

every three minutes). These methods are most appropriate for collecting time-averaged samples

(for example over the course of a fumigation event), or for verification of a positive PID reading (in

a similar capacity as gas detection tubes).

Following the MfE guidelines, “hazardous air pollutants” should be measured using USEPA

sampling methodologies7. The applicable USEPA methods for VOCs are:

Compendium Method TO-17, an active sampling method onto mixed bed charcoal tubes with

a detection limit of 0.2 to 25 parts per billion in air (ppb). This method allows complete

speciation of the volatiles captured on the sample tube, thereby pinpointing the concentration

of methyl bromide (and other compounds collected).

Other suitable USEPA methodologies are TO-14A and TO-15 which refer to the collection of

a gaseous sample into a specially prepared canister. This method has recently become more

realistic with canister supply and analysis now available in New Zealand and alleviates the

need to cool the samples as required for Method TO-17.

These sampling methods can provide time-averaged measurements of methyl bromide by sampling

at a constant rate over the time period being investigated (e.g., 1-hour, 8-hour, or 24-hour

averages), and may be useful for determining the average ambient concentrations of methyl

bromide over the course of a fumigation event. However, the use of this method without a real-

time analyzer will make it impossible to confirm concentrations and determine when monitoring

should stop as per the ERMA Decision.

3.6. General Advice on Instrument Selection

Although monitoring objectives are the major factor to consider, resource constraints and the

availability of skilled staff must also be considered. More advanced systems can provide

increasingly refined data, but are usually more complex and difficult to handle. Overall the

5 A glass tube containing an adsorbent material such as activated carbon or tenax for trapping VOCs in ambient air 6 Bags designed for collection of gas samples for subsequent analysis 7 Good-practice guide for air quality monitoring and data management, Ministry for the Environment, New Zealand, April 2009

PAGE 14

following combination of instruments and techniques appear to be the best balance of application

and cost although they may not be applicable depending on the nature of the fumigation site:

Handheld PIDs for boundary monitoring where there are expected to be no significant sources

of VOCs, apart from methyl bromide. These instruments are preferable due to their low cost,

and access to local supply, repair and calibration within New Zealand.

Methyl bromide-specific gas detection tubes should be used alongside PIDs to confirm the

presence of methyl bromide when significant and sustained readings are displayed on the PID.

In the event that a fumigation is occurring in an area that has been shown to have a high

background concentration of VOCs that interfere with measurement of methyl bromide with

PIDs, ambient air sampling methods followed by laboratory analysis as described in Section

3.5 should be used in combination with the PIDs.

A portable, affordable, durable and reliable methyl bromide-specific monitor would be preferable

to a PID. However, at present there is not a monitor that can meet these requirements.

A combination of PIDs and detection tubes can allow fumigation operators at difficult locations to

control fumigation venting if venting is required in poor dispersion conditions and the operator

feels the TEL could be breached. There is a wide variety of PIDs on the market. However, many

are not appropriate for these monitoring purposes. Users must be careful in their selection of a PID

to ensure that sensitivity, resolution, data logging capabilities and reliability conform to good

practice requirements.

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4. Site Selection

The selection of a monitoring site or location can have an effect on the resulting measurements of

contaminant levels and on achieving the monitoring objectives. The monitoring location must be

located where humans have the potential to be affected.

4.1. Site Numbers and Selection

sensitivity of the surrounding receiving environment, land use activities, local topography,

meteorological conditions of the area and the height and size of the fumigation point of ventilation.

Monitoring sites should be placed in locations at the buffer zone boundary where the highest likely

concentrations of methyl bromide would be expected.

EPA guidance8 recommends that three monitoring sites be selected when monitoring is initially

undertaken at a fumigation site. One site should be designated as a „worst-case‟ site and located at

the boundary of the buffer zone in the downwind direction, with the other two sites located on

either side to account for variation in wind direction of plus or minus 45 degrees. Alternatively,

one of the monitoring sites may be placed on the boundary of the buffer zone in the direction of

the nearest sensitive location, such as a residence or other place where the public may be. A good

rule of thumb is to use three downwind monitoring sites for the first couple of fumigations at a site

unless sensitive receptors, complex terrain or weather conditions dictate the need for more

locations. The number of locations should vary depending on the sensitivity of the surrounding

area, the size and scale of the fumigation operation and the influence of local topography.

Once a site has been monitored during fumigation events and it has been shown that the ambient air

concentrations have not exceeded the TELs during fumigations, then the number of monitoring

sites may be reduced based on site specific monitoring experience. For fumigations using less than

7 kg of methyl bromide one monitor may be sufficient (depending on forecasted wind conditions

and topographical influences) in a downwind direction. For fumigations using more than 7 kg of

methyl bromide, a minimum of two monitoring locations is suggested downwind from the

fumigation site. If sensitive locations are near the buffer zone then additional monitoring sites may

be needed at the buffer zone boundary in the direction of the sensitive sites. If monitoring has

previously been undertaken at the site, refer to the site‟s sampling location map if available and

utilize previous sampling locations taking into consideration the guidance set out in this document

or add another location if applicable. If a site specific map is not available one should be prepared

and should remain onsite.

8 EPA, Methyl Bromide Fumigations Post Reassessment Guidance for Fumigations, April 2011.

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4.1.1. The effect of land use activities on monitoring

This relates to the effect of human activities and vegetation in the area surrounding the fumigation

site. This includes the location of buildings and their height, location of trees, roads and other

sources of VOCs (e.g. paints, solvents, etc) in the vicinity which could affect PID measurements.

Ideally the site should not be unduly influenced by sources that are not being investigated. A

survey should be carried out to document the land-use activities within one kilometre radius of the

fumigation site. This could also include possible emission sources from large stands of trees or

marshland. The survey should record the location of industries, and residential properties and other

sensitive receptors. Sensitive receptors include schools, childcare centres, kindergartens, homes for

the elderly, medical centres, hospitals and possibly parks. Sensitivity may also vary with time of

day or night and with weather conditions. District Plan Zoning maps can be used to qualify the type

of activities expected in the immediate area.

Industries and uncovered log stacks that could release VOCs to air which can interfere with

monitoring when using PIDs should be identified. Such industries include panel and paint shops,

timber treatment plants, service stations, oil terminals, joiners, and sites with small boilers. These

sites should be recorded on a location map for the area around a monitoring site. In addition, if

PIDs are used for monitoring, roads need to be considered as they may present a source of VOC

emissions from vehicles operating or parked on the road. The storage of treated timber may be a

significant source of interfering solvents. These activities should be avoided if practicable when

selecting a monitoring location using PIDs.

Buildings, trees and walls located close to monitoring sites restrict airflows and as such should be

avoided. Free airflow around the sampling inlet is necessary to ensure representative sampling; for

this reason, sampling in a stagnant or sheltered micro-environment should be avoided. The

“Australia/New Zealand Standard AS/NZS 3580.1.1:2007 Method for sampling and analysis of

ambient air, Part 1.1: Guide to siting air monitoring equipment” provides guidance on the

separation distances that a monitoring location should be situated in respect to nearby buildings,

trees and walls. Figure 2 illustrates the separation distances required for an ambient monitoring site

under this standard.

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Figure 2 Separation Distances for Level Sampling Site

In summary the following separation distances area recommended:

The height of buildings or obstacles should be considered with the separation distance

calculated from the monitor to the top of the building times 2;

The distances to walls should be greater than 2 metres. If a high wall the same separation

distance as from a building should be used;

The sampling inlet should be located at least 20 metres away from tree drip-lines;

Ensure an unrestricted airflow of 270 degrees around the sample inlet (or 180 degrees if at the

side of a building); and

nsure an open sky angle of 120 degrees.

4.2. Geometric Considerations and Buffer Zones

The physical layout of fumigation locations, including the arrangement of buildings, roadways,

ramps, and interchanges must be considered during the selection process. Also the distance

downwind from the site should be considered in selecting monitoring locations. Monitoring

locations should be located at the edge of or just outside the buffer zone. Buffer zones are areas

that exclude public access and extend in every direction from the fumigation source including over

water. Minimum buffer zones are required by the NZ EPA any time methyl bromide is used and

PAGE 18

their size is dependent on the quantity of methyl bromide used. Table 2 indicates the minimum

buffer zone sizes that must be applied.

Table 2 Minimum Buffer Zones (Source: ERMA Decision 2010)

Use Minimum Buffer Zone

Ship‟s hold (1000 kg or more of methyl

bromide applied per site in an 24-hour period)

100 metres

Ship‟s hold (less than 1000 kg of methyl

bromide applied per site in an 24-hour period)

50 metres

Fumigation under sheets 50 metres

Containers (total volume of 77 m3 or more in

any 60 minute period)

25 metres

Containers (total volume of less than 77 m3 in

any 60 minute period)

10 metres

*77 m3 is the size of a standard shipping container

Buffer zones can be greater than those set out in Table 2 as long as the area is controlled and public

entry is restricted. The minimum buffer zones set out in Table 2 do not preclude Regional Councils,

Unitary Authorities or Port Authorities from setting larger buffer zones. Alternative buffer zones

(less than the minimums) may only be used if applied through a Code of Practice approved by the

EPA.

When considering the distance downwind to the monitoring location the actual height of the

venting and the volume of the discharge need to be taken into account. The venting height from

fumigation of a vessel‟s hold (around 4 to 8 metres above ground) is higher than that from a

container (approx 1.5 metres in the middle) and therefore the dispersion characteristics of the two

venting points will be different. Generally the higher the venting point is above ground the further

the plume9 will disperse downwind before it impacts on the ground. This point of impact is where

the highest concentration will typically occur. Meteorological conditions at the time of the venting

9 “Plume” is a term used by air quality professionals to describe the emissions from a source as they move

and disperse downwind, and its use here does not necessarily imply a constant emission of methyl bromide from the source.

PAGE 19

should also be considered as they will have an effect on how the plume behaves. In some locations

the ideal monitoring location may be located beyond the restricted area. In these cases two

monitors may be needed: one at the controlled area and one at the area of predicted highest

concentrations directly downwind.

4.3. Locations over Water

Locations over water that may be affected by methyl bromide fumigation releases include marina,

boat moorings and wharves. As it is not always practical to monitor at the buffer zone boundaries

provided in Table 2 when they occur over water, monitoring sites should be selected at the nearest

appropriate downwind location outside the buffer zone that is either on land or on an accessible

wharf. It is possible that moored boats near the buffer zone may be occupied during the fumigation

events, in which case it may be necessary to monitor at these locations.

4.4. Topography (Geographic Location)

The dispersion of methyl bromide from a fumigation site can be significantly altered by local

topographical features. Land features of the areas surrounding a fumigation site need to be

considered when selecting the number and location of monitoring sites. If the area is

predominately flat the influence of topography on dispersion of the ventilated fumigant is low. For

sites located in valleys, or next to steeply rising ground the effects of the terrain needs to be

considered when selecting monitoring sites. Valleys tend to channel the air flow and wind and

restricting horizontal dispersion. Concentrations can be the highest due to the poor dispersion

conditions and if the public are living or working in the base of valleys a monitoring location must

be selected to measure methyl bromide concentrations in this area. However if there are no persons

residing, working or likely to be in the area for extended periods on the valley floor, monitoring

locations may be better sited at residential properties part way up the valley wall.

Shorelines tend to produce frequent changes in airflow due to the land sea effect and as a result the

air can be more turbulent and the air flow can be subject to “sea breezes” and “land breezes”

depending on the time of day. In light winds the wind direction could shift 180 degrees during a

venting and illustrates the need for both upwind and downwind monitoring locations.

Monitoring sites on ridges should be avoided as they tend to be in clear air and can significantly

under estimate the high concentrations that occur in the valley floor.

Local meteorological effects are often tied to local geography, e.g., nearby mountains or coastal

locations. Consequently, selection of monitoring locations must include an assessment of the large-

scale geography, in addition to local-scale topography.

PAGE 20

4.5. Climate and Meteorology

The prevailing weather conditions and local topography will strongly influence the dispersion of air

contaminants in the atmosphere. Weather conditions are one of the most important factors

affecting spatial and temporal distributions of air contaminants, especially for short-term air

dispersion as associated with fumigation ventilation. Unusual weather conditions might lead to

higher or lower ambient air concentrations than would occur under normal weather conditions. For

example, inversion conditions would tend to restrict dispersion and result in higher ambient air

concentrations whereas an unstable atmosphere or high winds would increase dispersion.

Meteorological records should be reviewed to assess the following important parameters:

Prevailing seasonal wind direction;

Night and day-time wind patterns; and

Cold air flow wind directions.

Horizontal wind mixing in air has profound influences on the dispersion of methyl bromide

ventilated from a fumigation site. Consequently it has an influence on the selection of monitoring

locations. It is desirable to monitor at multiple points downwind concentrations of methyl bromide

and to take into account the wind speed and direction on the day that the monitoring occurs. As a

result a number of pre-determined sites will need to be selected for the site based on prevailing

wind directions and other atmospheric conditions, with the actual sites selected on the day of

monitoring.

The use of a published windrose (see Figure 5 for an example of a windrose) which shows for the

frequency of wind from that direction over the measurement period (in this example one year) and

the relative wind speeds for that direction over 16 sectors around the compass. A relevant

windrose should be used in the initial monitoring location selection process and should be updated

yearly.

Wind roses for New Zealand sites can be found at:

http://www.windfinder.com/windstats/windstatistic_map_new_zealand.htm

Some fumigation sites may not have good quality site specific meteorological data windroses, and

if a data from nearby location is used) then care must be taken as the conditions could be vastly

different even over a short distance. Based on the ERMA Decision wind direction and speed must

be recorded every 3 minutes during the fumigation venting.

If the fumigation site has complicated geography and weather conditions, specialist help should be

obtained to select appropriate sampling sites and to advise what sites are the best under a variety of

weather conditions.

PAGE 21

Figure 3 Example of a Wind Rose – Blenheim Airport 2002

WIND ROSE PLOT

WINDROSE BLENHEIM AIRPORT 2002

NORTH

SOUTH

WEST EAST

6%

12%

18%

24%

30%

Wind Speed (m/s)

> 11.06

8.49 - 11.06

5.40 - 8.49

3.34 - 5.40

1.80 - 3.34

0.51 - 1.80

COMPANY NAME

Sinclair Knight Merz Ltd

MODELER

Mira Chakraborty

PLOT YEAR-DATE-TIME

2002

Jan 1 - Dec 31

Midnight - 11 PM

DATE

8/10/2003

DISPLAY

Wind Speed

UNIT

m/s

CALM WINDS

0.87%

AVG. WIND SPEED

3.95 m/s

COMMENTS

ORIENTATION

Direction

(blowing from)

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

PAGE 22

4.6. Site Selection Checklist

A number of quick checks should be carried out when selecting a monitoring location and include

the following:

1) On a map of the area, determine distances from fumigation location to site boundary and to

nearest land-use activities and sensitive receptors. Mark out the required buffer zone on the

map as dictated by EPA requirements in Table 2, and consider options for monitoring near the

boundary;

2) Avoid sites that are adjacent to buildings, leafy vegetation, or walls as they could have

restricted airflows and in some cases can adsorb or absorb contaminants in air or release their

own contaminants;

3) If monitoring with PIDs, avoid sites near industry, large stands of trees, roads, uncovered log

stacks or activities that release VOCs as these monitoring devices cannot differentiate total

VOCs from methyl bromide and hence may result in higher concentrations being measured.

Pre-fumigation monitoring should be undertaken to determine if existing sources of VOCs are

likely to cause interference;

4) Determine the land-use activities in the area surrounding the fumigation site and identify any

potentially sensitive activities or areas close to the boundary where monitoring should occur;

5) Determine the prevailing wind directions and speeds for the area and preselect a number of

sampling locations that can be used depending on the wind direction on the day of monitoring.

These locations will be refined closer to the time of ventilation dependent on the forecast;

6) Estimate the height and size of the fumigation ventilation. As a general rule, the larger the

venting and the higher the venting point the further distant from the fumigation site the

monitoring locations should be located;

7) Determine based on the terrain of the area where cold air drainage flows will occur and the

direction of those flows and select the monitoring locations on the downward side of cold air

flows;

8) Avoid sites that could be affected by terrain features, e.g. close in to steep sided hills, on ridge

tops, and in small valley systems of a main valley where recirculation could occur;

9) For areas near the coast land sea breezes should be considered which could require both

upwind and downwind monitoring locations; and,

10) If the site has an established monitoring history compare the historical monitoring sites to

predicted wind direction to determine if these sites are appropriate for the current monitoring

event.

PAGE 23

Figure 4 Decision Tree: Determining Initial Sampling Site(s) Location

3 sample locations

(recommended)

Determine land use activities of

surrounding area and prevailing

wind direction

Small: <0.2 tonne of

fumigant

START

What is the size

and scale of the

fumigation?

2 sample locations

(recommended) 4 sample locations

(recommended)

Large: >1.0 tonnes of

fumigant

Medium: 0.2 to 1.0

tonnes of fumigant

YesNo

YesNo

Are there any steep

sided hills within the

monitoring boundary?Yes

Assess the potential of cold air

drainage within the area and

record localised meteorological

conditions during the sampling

No

Are there any

sensitive receptors

within 1.0 km?

Will forecasted wind

blow towards

sensitive receptors?

Assess the terrain of

the area – valleys,

steep hills etc

Select as

monitoring

location at

boundary

downwind of

fumigation

Select

monitoring

location at

boundary

downwind of

fumigation

PAGE 24

Figure 5 Decision Tree Monitoring Site(s) Location, Measurement Method and Tools

Is the location close

to potential VOC

sources?

No

Yes

Monitoring

location

acceptable.

Install PID as

instructed.

Seek

alternative

location at

boundary

downwind of

fumigation

Is the location close

to buildings, walls or

trees?

No

Yes

Is the location close

to steep hills?

No

Location relative

to winds Upwind

Seek alternative

location at least 10m

from trees and a

distance of 2 times

the height of the

nearest building.

Is the location close

to buildings, walls,

trees or steep hills?

Yes

No

Is MeBr Specific

sampling going to be

used?

Yes

No

Seek alternative

location away

from VOC

sources

Monitoring

location

acceptable.

Install MeBr

specific

equipment as

instructed

Is the location

upwind or downwind

of the fumigation?

Downwind

Downwind

Upwind

Yes

START

Assess the potential of cold air

drainage within the area and

record localised

meteorological conditions

during the sampling

Return to

START

Light wind

or land

sea

changes

Select

monitoring

location at

boundary close

to sensitive

receptors.

If location is critical for

monitoring sensitive

receptor(s)

PAGE 25

5. Sampling and Data Recording

5.1. Introduction

This section details the importance of recording data collected before, during, and after sampling,

and data produced by real time analysers. Field Sampling Data Sheets for sampling techniques

discussed in this document are presented in Appendix A; and are referred to in this section as the

“data sheet”. Subsection 5.5 presents a flow diagram for this section. An example of an ambient air

monitoring programme carried out during a methyl bromide fumigation ventilation in NZ is

included as Appendix B.

5.2. EPA Data Collection Requirements

New controls were added for methyl bromide use that directly relate to monitoring during

fumigation venting following the ERMA Decision. The requirements for collecting data during

methyl bromide fumigations are found in Table C2 of Appendix C of the Decision. This

information is summarised in

PAGE 26

Table 3 below.

The Decision goes on to state that data collection for fumigation without MeBr recapture must be

begun at or before the start of the ventilation and continue until the exposure level is below 0.05

ppm for at least 15 minutes where 7 kg or more of methyl bromide is applied in a one-hour period,

or for 3 minutes where less than 7 kg of methyl bromide is applied in a one hour period.

PAGE 27

Table 3 Required Data Collection by ERMA Decision for Methyl Bromide Fumigations

Scenario Data Collection Required

Fumigation with MeBr recapture

(a) date and time of each application and recapture; (b) location where the methyl bromide was applied and recaptured; (c) amount of methyl bromide applied and recaptured; (d) type of enclosed space to which the methyl bromide was applied; (e) capacity of the enclosed space; and (f) name of the person using methyl bromide and the physical address of their place of work.

Fumigation without MeBr recapture

(a) date and time of each application and ventilation; (b) amount of methyl bromide applied; (c) location where the methyl bromide was applied and ventilated; (d) wind speed and direction every 3 minutes at the location during ventilation; (e) type of enclosed space to which the methyl bromide was applied; (f) capacity of the enclosed space; (g) name of the person using methyl bromide and the physical address of their place of work; (h) for each monitoring location, exposure levels; and (i) for each monitoring location, the type and location of the monitoring equipment used to record the exposure levels.

Any discharge of MeBr (a) date and time of each discharge; (b) approximate amount of methyl bromide discharged; (c) location where the methyl bromide was discharged; (d) approximate wind speed and direction at the location when the discharge occurred; (e) where the discharge occurred from; (f) the reason why the discharge occurred; (g) capacity of the enclosed space; and (h) name of the person using methyl bromide and the physical address of their place of work

5.3. Pre-Sampling

Prior to sampling it is important to follow the direction provided in the previous section to

determine sampling locations. Record on the Field Sampling Data Sheet all relevant information

pertaining to the site, including locations of the fumigation and selected sampling sites. Room is

provided on the data sheet to sketch the area and annotate sample locations. However, a detailed

location map or aerial photograph should be used to pinpoint the monitoring locations. Additional

space is also provided to detail the topographical nature of the area which is important in valleys,

PAGE 28

steep sided bays and sounds. Figure 6 depicts an example of sample location selection at a port in

New Zealand.

Figure 6 Example of Site Perimeter and Sample Locations

After sketching the area, investigate the actual weather conditions and record the local conditions

four hours prior to the fumigation ventilation stage. Repeat this again 1 hour prior to the

ventilation stage. A change in the wind direction will affect the positioning of monitoring sites in

which case the decision tree diagrams will again have to be consulted to determine appropriate

sampling locations.

It is important to maintain a running sampling location map which will identify a record of

monitoring locations for a fumigation site. This sampling location map must be updated for all

subsequent fumigation venting events. While additional locations may be added over time, a

historic sampling location cannot be removed and the numbering or labelling integrity must be

maintained. This will be essential for determining annual TELs, especially if different technicians

undertake the monitoring.

Follow the manufacturer‟s instructions for the monitoring equipment, and record all information

relating to the equipment and calibration on the data sheet. It is also important to record local

meteorological conditions at each sample location upon sampler deployment. The data sheet allows

room for this data to be recorded. The sequence below specifically applies to monitoring using

PIDs together with gas detection tubes, but can be extended for use with alternative sampling

methodologies:

3

1

4

2

6

3

5

PAGE 29

1) On arrival at the site designate an operations centre/clean-up area, and perform a zero and span

check on all instruments by applying a certified calibration gas for 5 to 10 seconds, and a

charcoal filter for reading zero air. If the instrument reading is outside of ±10% of the span

gas concentration, or are not reading zero for the zero gas, then perform a full calibration.

Record calibration checks and any full calibrations performed on the data sheet for each unit.

2) Install the sampling inlet of all monitoring equipment as far as possible at 1.5m above local

ground level at the pre-determined sampling locations unless topography and fumigation

ventilation points dictate a more appropriate height.

3) Install instruments at the pre-determined sample locations and begin monitoring at least 15

minutes prior to the beginning of the venting stage of the fumigation. Record sample/sampler

number(s), location(s) and sampling start time(s).

5.4. During Sampling

1) Run all the sampling equipment prior to, during, and following the fumigation venting stage.

Note the venting time(s). If using active samplers such as sorbent tubes or canisters, sample for

1 hour per sample, after which additional tubes/canisters should be used for subsequent one

hour periods.

2) During monitoring the technician must “walk the perimeter” a minimum of once an hour, and

preferably two to three times, checking all sampling equipment for errors, battery life and peak

readings. Unless monitors are linked for remote monitoring, technicians should record the peak

reading and reset peak readings (if possible) during each walk around. During this time it is

also important to measure and record the meteorological conditions at each sampling location,

either by handheld anemometer or by estimating wind speeds (estimating wind speeds should

only be undertaken by an experienced technician).

3) If during sampling a PID displays readings that indicate the presence of VOCs, then a gas

detection tube should be used to confirm that the reading is methyl bromide and not another

VOC or due to instrument drift. If the methyl bromide gas detection tube does not show a

positive result, and the PID continues to record concentrations above zero, a carbon filter

should be attached to the instrument inlet for 5 to 10 seconds to discount the presence of other

VOCs, thereby indicating instrument drift. A backup PID can also help confirm drift and can

be used to replace an instrument that has drifted and needs to be cleaned and re-calibrated prior

to being re-deployed.

4) During the monitoring period note any significant events that may positively or negatively

affect or influence the sampling results, e.g. the presence of vehicle exhaust fumes or the

presence of volatile organic compounds (VOCs) including any nearby treated timber or log

stacks.

PAGE 30

5) Once venting is completed note the time that the ventilation stopped. Monitoring shall

continue until the concentrations of methyl bromide are below 0.05 ppm for at least 15 minutes

if the fumigation used more than 7 kg of methyl bromide or for three minutes if the fumigation

used less than 7 kg. Return to the designated clean-up area for post-sampling calibration

checks. If active sampling methods are being used due to VOC interference a good rule of

thumb is to continue monitoring one hour following the last ventilation of a log stack or

container or two hours following a ship‟s hold.

5.5. Post-Sampling and Sample Handling

At the end of the sampling period all active sampling equipment (apart from gas detection tubes

and pumps) should be checked in accordance with the method used. Checks are as follows:

Methyl bromide specific real time samplers – refer to the manufacturers instruction for

performing post sampling calibrations or checks;

PIDs – Check the instrument against calibration gas used in the initial pre-sampling calibration

to determine calibration drift over the sampling period;

Methyl bromide specific active sampling method (e.g. USEPA method TO-17) – Check the

flow rate through the whole sampling system prior to dismantling. The end flow rate must be

within 10% of the start flow rate to meet the quality requirements set out in the method; and,

USEPA method TO-15 – No checks required from the operator, however, data relating to the

vacuum of the evacuated cylinder will be recorded.

Sample and data handling is a critical stage of the sampling protocol. Data from PIDs or other real-

time sampling devices should be downloaded immediately after post sample checks and the data

stored in a secure non-volatile memory for future interrogation. It is advisable to store the data in at

least two systems to protect against loss or corruption (a printed hard copy provides added

security). If another analyzer not addressed in this section is used please refer to the applicable

method and operation instructions to ensure the quality requirements are met.

Active samples collected in the field requiring further analysis should be handled as follows:

All samples must be clearly identified

After each sample is collected a “chain of custody” form should be filled in detailing all

information relating to the sample and analysis required. One copy should be included with the

samples and one retained and filed.

If method TO-17 is used samples should be immediately sealed and placed on ice to reduce

volatilisation of methyl bromide or other VOCs collected on the media.

PAGE 31

It is important to maintain the samples below the boiling point of the target compound, hence

an accredited local laboratory should be selected to reduce shipping times and the possibility

of exposure to elevated temperatures.

It is common practice to place an ambient temperature logger in the shipping case in order to

determine the maximum temperature to which the samples have been exposed.

Only IANZ accredited laboratories should be used for analysis unless another form of quality

assurance is available.

PAGE 32

Figure 7 Pre, During and Post Sampling Flow Diagram

Place samplers at the pre

selected sample locations

Conduct calibration check or full

calibration as necessary.

Synchronise all clocks to a common

time. Ensure datalogging feature is

enabled.

PID

Record zero and span

results etc

Calibrate flow rate through whole

sampling system if directed by the

method

If meteorological

conditions are

acceptable start

sampling prior to

MeBr release

Active Sampling (TO-15,

TO-17)

For each location record the location number,

sampler, start/exposure time, meteorological

conditions etc. Wind speed and direction

should be recorded every 3 minutes near the

venting site.

Follow manufacturer instructions and ensure that you are competent in the use of the

equipment before proceeding further

Select method based on

previous flow diagram

During sampling walk the

perimeter once per hour

checking the samplers and

recording met conditions and

peak readings

Note the sampling stop time

at each location.

If PID shows positive reading, confirm

with colorimetric methyl bromide

monitoring tubes. If tubes indicate no

MeBr is present, use a charcoal tube or

backup PID to rule out drift PID

baseline drift. If drift is confirmed

replace the PID.

Perform span gas check and

record results

Check the end flow rate through

TO-17 train and compare against

initial flow rate

TO-17

PID

Download data from PIDs to

PC.

MeBr specific real

time analyser

Label all TO-17 samples,

prepare a chain of custody,

pack the samples in ice with

temperature sensor, and send

to laboratory for analysis.

Label all TO-15 samples,

prepare a chain of custody,

and send samples to the

laboratory for analysis

TO-15

If using PIDs or

other real time

monitors stop

sampling when

MeBr readings

are <0.05 ppm

for 3 minutes.

If using PIDs or

other real time

monitors stop

when MeBr

readings are

<0.05 ppm for

15 minutes.

>7kg MeBr<7kg MeBr

Carry out pre sampling calibrations

zero/span checks as per the

manufacturers specifications.

PAGE 33

5.6. Further Information

5.6.1. Calibration

Most air quality monitoring equipment (including data loggers) must be calibrated at specified

intervals to minimise instrument bias and drift. A record of the calibration procedures and history

should be kept and be available upon request. Good data quality depends on adequate calibration of

the equipment. For an analytical instrument for measuring compounds in air, a calibration involves

setting the reading of a monitor to the known concentration of a compound in a calibration

standard. A calibration check may be performed to confirm that the calibration for that instrument

is still valid within a permitted range of variance (typically ±10% of the calibration gas value).

Calibrations should be conducted in accordance with manufacturer‟s recommendations for the

instrument. PIDs shall be calibrated within no more than three months prior to use.

Calibration checks shall be adopted along with any specific requirements for the particular standard

monitoring method used. Span and zero checks should be conducted relatively frequently (some

modern equipment has an automated facility allowing this to occur every 24 hours, otherwise it

should be carried out at least once a month or prior to a sampling episode/event), but in general

these cannot replace true multi-point calibrations. If the zero and span checks are greater than 10%

of the reference gas then the instrument shall be calibrated prior to use.

5.6.2. Data Logging

Wherever possible, air quality data should be recorded automatically, with as high a time resolution

as is practicable. Data loggers should be configured to provide data as 1-minute averages and shall

log data no less than every three minutes. The data is to be downloaded from the loggers either

manually or via telemetry on an event basis (depending on data logger capacity). The raw data

should then be saved on disk, archived, and a copy transferred to PC for quality assurance. In

general, averaging and processing should occur later, rather than within the data logger to preserve

the resolution of the raw data. Data should be averaged to rolling 1-hour and 24-hour values for

reporting purposes.

5.6.3. Quality assurance and quality control (QA/QC)

Quality assurance and quality control (QA/QC) is an essential part of any air monitoring system. It

is a programme of activities that ensures that measurements meet defined and appropriate standards

of quality, with a stated level of confidence. QA/QC activities ensure that measurements comply

with relevant guidelines specific to the data quality objectives for the monitoring programme. In

other words, QA/QC ensures that data are fit for the purpose. This includes but is not limited to:

Measurements are accurate, precise and credible;

PAGE 34

Data are representative of ambient or exposure conditions;

Results are comparable and traceable;

Measurements are consistent over time; and,

Meteorological conditions recorded.

5.6.4. Instrument Use

Even the best maintained instruments can fail during monitoring events and it is important to know

what to do if an instrument does fail during fumigation ventilation. This section discusses steps to

take to help avoid faults and actions to take if a fault does occur. While this section is only directly

applicable to PIDs and sampling pumps, the concepts behind these recommendations can be

applied to other equipment used to monitor methyl bromide in ambient air.

Hiring equipment

If the equipment required to monitor fumigation ventilation is hired from an equipment supplier, it

is important to let the supplier know that you will be monitoring for compliance purposes and at

very low concentrations of methyl bromide. Ask the supplier to provide the most recently serviced

equipment available including any calibration documentation and data download cables if

applicable. An additional pump or PID should be hired to have on hand should an instrument fail or

drift. A good rule of thumb is to have an additional PID for every two to three locations that will be

monitored and a single replacement pump if method TO-17 is used for monitoring.

Calibration

Equipment shipped from a vendor should be checked at the earliest opportunity to ensure that all

the equipment is in working order prior to going on-site. For PIDs and other real time samplers

both pre and post zero and span calibration checks are required to meet quality assurance

requirements. Generally suppliers will calibrate the instrument prior to dispatch so in these cases a

simple zero and span gas calibration check will provide a suitable level of confidence. Make

certain there is adequate calibration gas (e.g. isobutylene) to perform the pre and post calibration

checks for all instruments used in the monitoring. If the zero and span checks are greater than 10%

of the reference gas then the instrument shall be recalibrated prior to use. Remember that the

automatic correction factor of 1.7 for methyl bromide may be active and will return a 170 ppmv

reading when using 100 ppm reference gas.

Batteries

All equipment should be checked to ensure battery life is sufficient to monitor both prior to and

following the fumigation venting. Extra battery packs should be ordered if the fumigation

PAGE 35

ventilation event could potentially continue beyond the battery life of the instrument or pump. If

the battery life is less than 90% the batteries should be replaced or charged as per the

manufacturer‟s recommendations.

Equipment failure

If equipment does fail during or prior to fumigation venting the ventilation should be delayed until

the fault can be repaired or the equipment can be replaced.

Instrument drift

PIDs are susceptible to drift caused by moisture and should be interrogated immediately if drift is

suspected. It is vitally important that the instrument is replaced as soon as practicable if drift is

suspected.

PAGE 36

6. Presentation of Results

6.1. Introduction

This section discusses the presentation of data collected before, during and after sampling and data

collected by PIDs and by other sampling methods. Included are examples of tables which may be

used to present meteorological data and ambient air sampling results and data processing guidance.

For further guidance on data processing and rolling average calculation refer to the MFE Good

Practice Guide for Air Quality Monitoring and Data Management 200910

, the ERMA Decision and

the document Methyl bromide fumigations, Post-reassessment guidance for fumigators: EPA New

Zealand, April 2011.

6.2. Meteorological Data

Meteorological conditions observed, measured and recorded during the sampling period are

important in helping to interpret concentrations measured at specific locations. Data such as wind

direction, wind speed, sunlight strength and cloud cover are important. There are generally two

separate meteorological data sets collected on site during fumigation:

Data recorded manually by visual and portable electronic observations (useful for localised

conditions at sample locations); and

Data recorded automatically by electronic observations at an established meteorological site

(useful for large scale conditions).

Data sets are important and should be collected and presented in the final fumigation monitoring

report. Tables 4 and 5 are examples of how the meteorological data may be presented.

Meteorological data must be collected every three minutes during the ventilation but can be

reported in a variety of averaging times.

10 Good Practice Guide for air quality monitoring and data management: Ministry for the Environment 2009.

PAGE 37

Table 4 Example of Meteorological Conditions Experienced

Date Time Location

Estimated Wind Direction (blowing from)

Estimated Surface Wind speed (m/s)

Sunlight Strength (slight, moderate, strong or night time)

Cloud Cover

Beaufort Scale

11

15/02/09 23:30 Wharf W / NW < 2 Night time Clear sky – no cloud

2

16/02/09 03:20 Wharf E / NE 2 – 3 Night time >50 %

3

16/02/09 03:50

Lookout – south-southeast of the wharf

E / NE (when apparent)

< 2 (when apparent)

Night time >50 %

1

Table 5 Example of Meteorological Data Measured at Weather Station

Date Time Wind Direction (degrees,

360 = North) Wind Speed (m/s)

15/02/2009 2300 352 15.0

15/02/2009 2315 018 10.0

15/02/2009 2330 024 10.0

15/02/2009 2345 023 9.0

16/02/2009 0000 035 6.0

16/02/2009 0015 036 3.0

16/02/2009 0030 049 8.0

16/02/2009 0045 142 4.0

16/02/2009 0100 148 5.0

16/02/2009 0115 151 6.0

6.3. Results of Monitoring

It is important to numerically link all aspects of the sampling for ease of reference. This can be

achieved by using specific numbers for each sample location marked on the site plan (see Table 6

for sample location numbering example) right through to the results presentation. All results from

PIDs should be presented as parts per million by volume (ppmv) as a 1 hour rolling average and as

a 24 hour rolling average. In the case of PIDs the results should be corrected for the target

compound by using the experimentally determined correction factors relative to the calibration gas.

PIDs are typically calibrated with isobutylene calibration gas, and the instrument manuals will

11 http://en.wikipedia.org/wiki/Beaufort_scale

PAGE 38

contain a table of correction factors for individual VOCs which must be applied to the compound

of interest.

For example:

The correction factor for methyl bromide at the setting is 1.7 for an isobutylene-calibrated PID. If

the PID reads 1.0 ppm, then this equates to 1.7 ppm of methyl bromide. Some PIDs provide an

option for the correction factor to be applied internally, in which case the reading will be correctly

referenced to methyl bromide.

All results from extractive samples collected and sent for laboratory analysis will have to be

converted from laboratory mass or concentration results and presented as parts per million by

volume (ppmv) as 1 hour maximum rolling averages and 24 hour rolling averages per site.

Laboratory results and sample volumes should be included in the ppmv results table.

Table 6 below is an example of how the monitoring location data could be presented, Table 7 is an

example of monitoring locations and monitors used and Table 8 is an example of how the

maximum 1-hour average and 24-hour average (24-hour rolling average if venting extends beyond

24-hours) concentration results at each location could be presented.

Table 6 Example of Monitoring Locations

Sampling location

Location description Height above sea level (m)

Distance from Fumigation Site (m)

Reason for site selection

1 Southern ground level security gate

<5.0 450 Public access way close to gate, public exposure possible

2 Southern hillside fence location near lookout

30 480 Close to public scenic lookout, public exposure highly probable

3 Eastern ground level security gate

10 560 Ground level access road, public exposure possible

4 North-eastern hillside reserve fence location

12 460 To capture possible elevated plume and swirling winds

5 Upwind location 3 100 Upwind if wind shifts

6 Downwind land water boundary

3 100 Closest downwind land water boundary

PAGE 39

Table 7 Example of Monitoring Locations and Details of Monitors Used

Date Monitoring Period

Monitoring Location (Monitor ID)

PID ID Make of PID

Calibration

01/04/11

00:15 – 05:05 1 (B) 592-904391 (Port Hired)

MiniRAE 3000

Full prior, spot onsite

00:15 – 05:00 2 (C) 592-903608 (Port Hired)

MiniRAE 3000

Full prior, spot onsite

00:15 – 05:03 3 (D) 900775 (SKM Owned)

MiniRAE 2000

Full onsite

00:15 – 01:24 4 (F) 110-1010316 (Port Hired)

MiniRAE 2000

Full onsite

01:25 – 02:27 4 (G) 110-007539 (Port Hired)

MiniRAE 2000

Full onsite

02:28 – 04:56 4 (H) 095-108042 (Port Hired)

MiniRAE Multi

Full prior, spot onsite

00:15 – 04:55 5 (E) 110-014975 (Port Hired)

MiniRAE 2000

Full onsite

00:17 – 05:11 6 (I) 095-108039 (Port Hired)

MiniRAE Multi

Full prior, spot onsite

*The monitor at location 4 was replaced twice due to instrument drift.

Table 8 Example of PID Total VOCs Ambient Air Monitoring Results – Reported as Methyl Bromide

Date Monitoring Time Monitoring Location #

Maximum 1-hr rolling average VOC concentrations (based on built in correction factor of 1.7 for methyl bromide) (ppmv)

24-hr average VOC concentrations (based on a correction factor of 1.7 for methyl bromide) (ppmv)

01/04/11 00:15 – 05:05 1 0.24 0.02

00:15 – 05:00 2 0.00 0.00

00:15 – 05:03 3 0.00 0.00

00:15 – 04:55 4 0.01 0.01

00:15 – 01:22 5 0.00 0.00

00:17 – 05:11 6 0.11 0.01

PAGE 40

6.4. Calculation of Time-Averaged Methyl Bromide Concentrations

The following is updated guidance for determining time-averaged concentrations of methyl

bromide from ambient air monitoring data near methyl bromide fumigations. 1-hour, 24-hour and

annual average concentrations of methyl bromide must be determined for comparison with the

TELs and to satisfy reporting requirements of the EPA as described in the Methyl Bromide

Fumigations: Post-reassessment Guidance for Fumigators (EPA, April 2011).

These recommendations are made with the assumption that monitoring is conducted using PIDs at

the buffer zones around methyl bromide fumigations. PIDs are at present the best option available

for ambient air monitoring of methyl bromide fumigations due to their providing direct and

continuous readings and their affordability. This makes them appropriate for detecting

concentrations against the 1 hour TEL and the 24 hour TEL (1ppm and 0.333ppm respectively).

However the instruments lack the sensitivity to detect methyl bromide at concentrations relevant to

chronic exposure levels of methyl bromide when multiple daily ventilations occur on a regular

basis, i.e. the annual TEL for methyl bromide is 0.0013 ppm, while the lowest reading provided by

most PIDs is 0.1 ppm.

6.4.1. Calculating 1-hour and 24-hour Averages

1-hour and 24-hour average concentrations are calculated assuming methyl bromide concentrations

of zero during the times that monitoring did not occur. As PID readings are typically collected as

1-minute averages, a 1-hour average would be calculated by summing all PID readings during the

1-hour period of interest and dividing by 60. 24-hour averages may be calculated either by

averaging the 1-minute data or by averaging the 1-hour averages over that 24-hour period.

If the monitor reads zero during the ventilation period it is possible that methyl bromide from the

fumigation is present at levels below the instrument level of detection. If there were no measured

readings at a monitoring site on a given day, then the monitoring record should state that the 1 hour

and 24 hour averages were not calculated as there were no measured readings at that site on that

day while stating the limit of detection of the monitoring equipment (typically 0.1 ppm for PIDs).

For fumigation monitoring events in which methyl bromide is measured during the ventilation

period, it is recommended to calculate 1-hour and 24-hour averages by assuming concentrations of

one-half the level of detection for the non-detect (or zero) readings immediately before and after

the detected readings. Assuming a level of detection for PIDs of 0.1 ppm, a value of 0.05 ppm may

therefore be assumed for non-detect readings immediately before and after measured readings of

methyl bromide. An example showing the calculation of 1-hour and 24-hour average

concentrations from monitoring data collected over a 30-minute period is shown in Table 1 from a

fumigation using less than 7kg methyl bromide.

PAGE 41

Table 9 Example Calculation of 1-hour and 24-hour Averages, Using 1/2 the Level of Detection for Non-Detect Readings when methyl bromide is detected

Time Direct Readings (ppm) Adjusted Readings for Averaging (ppm)

Ventilation start time

10:00 0.0 0

10:03 0.0 0.05

10:06 0.1 0.1

10:09 0.5 0.5

10:12 0.5 0.5

10:15 1.0 1.0

10:18 0.1 0.1

10:21 0.0 0.05

10:24 0.0 0

10:27 0.0 0

10:30 0.0 0

1-hour average (ppm): (sum of adjusted readings/20) 0.11

24-hour average (ppm): (sum of 1-hour averages/24) 0.005

6.4.2. Calculating Annual Averages

Only those days in which methyl bromide was positively measured need be considered for the

calculation of annual averages.

If there were no measured readings at a monitoring site over the course of the year, then the annual

report need only state that the annual average was not calculated as there were no measured

readings at that site.

Measured readings may be discounted if they can be shown to be due to instrument malfunction

(e.g., baseline drift) or from interferences with other VOCs. Instrument malfunction can be shown

by comparison with a second PID at the same location, while ruling out interferences with other

VOCs must be proven by methyl-bromide specific methods such as using Gastec/Drager

colorimetric tubes.

If there were confirmed measured readings of methyl bromide at a monitoring site during the

course of the year, then the 24-hour averages only for those days in which the measured readings

occurred should be used to calculate the annual average. All other days are assumed to have

methyl bromide concentrations of zero for the purposes of determining the annual average,

regardless of whether fumigations occurred at the site on those days.

PAGE 42

Table 2 provides an example calculation of an annual average from 24-hour average concentrations

determined as described in Section 2. The “Methyl Bromide Detected?” column in Table 2 states

whether methyl bromide was detected on that particular day. Only these days are included in the

next column for determining the annual average. These values are then summed and divided by

365 to calculate the annual average as per the EPA Post Reassessment Guidance for Fumigators.

Table 10 Example Calculation of Annual Averages from 24-hour Averages

Date 24-hour Averages (ppm)

Methyl Bromide Detected?

Value For Annual Average calculation (ppm)

21/1/11 NC1 No 0

28/1/11 NC No 0

3/2/11 0.0208 Yes 0.021

4/2/11 0.0167 Yes 0.017

5/3/11 NC No 0

6/4/11 0.000 No 0

4/5/11 0.0879 Yes 0.088

7/6/11 NC No 0

7/7/11 0.0284 Yes 0.028

7/8/11 NC No 0

10/9/11 0.0552 Yes 0.055

12/11/11 NC No 0

Sum of 24-hour averages 0.209

Annual Average 0.0006 1 No methyl bromide was detected on this day, so the 24 Hour average was not calculated. The limit of

detection of the monitoring equipment was 0.1ppm.

The practise of using the ½ level of detection of 0.05 ppm in calculating annual averages has the

potential to result in overestimations of annual average concentrations of methyl bromide,

particularly at sites which perform a large number of fumigations per year. These sites may wish to

supplement the monitoring regime by longer-term sampling and analytical methods with lower

levels of detection than can be provided by PIDs. For example, a series of canister samples may be

collected over consecutive 4 week periods and analysed for methyl bromide by GC-MS via Method

TO-15. The 4-week sample results can then be averaged to determine an annual average

concentration of methyl bromide at the site. Monitoring sites for long-term sampling should be

located so that they are downwind of the fumigation areas as much as is practicable in order to

assess the maximum concentrations resulting from the fumigations.

PAGE 43

6.4.3. Reporting Averages

Averages must be reported in a format that is relevant to measured concentrations and the exposure

limits being reported against, and must include units of concentration:

The 1 hour TEL is 1ppm (3.9 mg/m3), so examples of a recorded 1 hour exposure level would

be: 0.05 ppm methyl bromide or 0.2 mg/m3 methyl bromide.

The 24 hour TEL is 0.333 ppm (1.3 mg/m3), so examples of a recorded 24 hour exposure level

would be: 0.055 ppm methyl bromide or 0.2 mg/m3 methyl bromide.

The chronic (annual average) TEL is 0.0013 ppm (0.005 mg/ m3), so examples of a recorded

24 hour exposure level would be: 0.0055 ppm methyl bromide or 0.021 mg/m3 methyl

bromide.

6.5. Conclusion of Results

After the presentation of the meteorological data and contaminant concentration results, a

conclusion shall be reached relating to the relevant ambient air standards. Any measurements

showing significant concentrations of MeBr or other VOCs should be related to the timing of the

ventilation and wind direction if it is possible they were caused by the fumigation. Any non-zero

readings due to instrument drift or by interfering VOCs should also be described.

A report outlining the methodology and results of the ambient air monitoring containing all

relevant data as required by the ERMA Decision shall be created for monitoring of a fumigation

venting event.

Locations using more than 500 kg/year of methyl bromide per calendar year without re-capture

technology must also prepare an annual report outlining their air quality monitoring programme

including all required information as set out in Section 16.8.4 of the ERMA Decision. This report

must be provided to the EPA, the Department of Labour and the local Medical Officer of Health by

the 30th of June the following year and should be made available to the public upon request.

Any breaches of the 1-hour or 24-hour TELs outlined in Section 2.2 of this GPG must be reported

to the Department of Labour and relevant Medical Officer of Health as soon as practicable but

within 5 working days. An example of a notification sheet can be found at Appendix 2 of the

following document:

http://www.epa.govt.nz/Publications/Methyl%20bromide%20guidance%2018.04.pdf

All monitoring data must be kept for a period of seven years after the fumigation and must be made

available to any enforcement agency upon request.

PAGE 44

7. References

1. Decision on Application for the Reassessment of a Hazardous Substance under Section 63 of the Hazardous Substance and New Organisms ACT 1996 Name of substances: Methyl Bromide and formulated substances containing methyl bromide. Application Number: HRC08002, Environmental Risk Management Authority, New Zealand. 28 October 2010. (http://archive.ermanz.govt.nz/resources/publications/pdfs/Methyl%20Bromide%20Reassessment

%20Application.pdf) 2. Methyl Bromide Fumigations Post-Reassessment Guide for Fumigators, EPA, April 2011. 3. MiniRAE 2000 Portable VOC Monitor PGM-7600, Operation and Maintenance Manual.

RAE Systems 2005. 4. Good practice guide for air quality monitoring and data management, Ministry for the

Environment, New Zealand, April 2009. 5. Methyl Bromide, NIOSH 25020 Issue 2, 1996. 6. http://www.wunderground .com/US/FL/Boca_Raton.html 7. Methyl bromide fumigations, Post-reassessment guidance for fumigators. Environmental

Protection Authority, New Zealand, April 2011. 8. http://en.wikipedia.org/wiki/Beaufort_scale 9. Australian/New Zealand Standard 3580.1.1:2007 Method for sampling and analysis of

ambient air, Part 1.1: Guide to siting air monitoring equipment. 10. Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient

Air, Second Edition, Compendium Method TO-17, Determination of Volatile Organic Compounds in Ambient Air Using Active Sampling Onto Sorbent Tubes. USEPA, January 1999.

11. Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, Second Edition, Compendium Method TO-15, Determination of Volatile Organic Compounds (VOCs) in Air Collected In Specially-Prepared Canisters And Analyzed By Gas Chromatography/Mass Spectrometry (GC/MS). USEPA, January 1999.

PAGE 45

Appendix A Ambient Monitoring Field Data Sheets

PAGE 46

Ambient Air Monitoring: Site Evaluation Form

Site details (name, location etc)

Exporter details (name, contact person etc)

Fumigator details (company name, contact person and physical address of place of work)

Goods under fumigation (name, quantity etc) type of enclosed space (stacks, holds, containers) and capacity of enclosed space.

Type of fumigant used and quantity

Date and time fumigant introduced

Date and time fumigant vented (fill in retrospectively)

Relevant ambient air quality guidelines

Security boundary or Buffer Zone monitoring (please state type and attach a site plan of the monitoring locations)

Closest sensitive receptor and distance from monitoring boundary and centre of fumigation site

Were there any uncontrolled discharges of the fumigant? ( If so provide the following details; date and time of discharge, discharge location, estimated quantity discharged, why the discharge occurred, circumstances and wind direction during the discharge)

PAGE 47

Plan sketch/photograph/diagram of site including buffer zone boundary

Relief sketch/photograph/diagram of site

PAGE 48

Forecasted (expected) Weather Conditions for Proposed Period of Monitoring

Prevailing Wind direction (blowing

from)

Ambient temperature (OC)

Local Weather Conditions 4 hours prior to fumigant release

Prevailing wind direction (blowing from)

Cloud cover (> or <50%)

Wind speed (m/s) Daytime sunlight strength (strong, moderate, slight or night time)

Beaufort wind force scale (1-12) Ambient temperature (OC)

Local Weather Conditions 1 hour prior to fumigant release (annotate on plan

sketch/photograph/diagram)

Prevailing wind direction (blowing

from)

Cloud cover (> or <50%)

Wind speed (m/s) Daytime sunlight strength (strong,

moderate, slight or night time)

Beaufort wind force scale (1-12) Ambient temperature (OC)

Attach a copy of wind direction and speed data recorded every 3 minutes during venting. Include

the type of equipment used to record the data.

PAGE 49

Ambient Air Monitoring: Sampling Methodology and Location

Ambient air monitoring equipment used and

technique (e.g. PID, gas detection tube,

canister sample)

Applicable method or standard of sampling

Method of laboratory analysis (if applicable,

e.g. TO-15)

Estimated duration of sampling

Number of sample locations

Analyser section

Analyser Information (For Real Time Sampling Only)

Make Model Equipment

type

Equipment

ID

Mode Gas

Selection

Correction

Factor

Logging

Interval

Notes:

PAGE 50

Notes:

Real Time Sampling

Pre-sampling calibration

Equipment

type

Equipment ID Span gas type

and

concentration

(ppm)

Pre-cal

reading

Zero

reading

Span

reading

Zero

reading

Post-cal

reading

Sample location information – mark each sample location on plan sketch with and

associated sample number

Sample

Location

Number

Location/Name Equipment

type and ID

Wind speed

and direction

at sample

installation

Distance

from

fumigated

goods

Start

date

and

time

End date

and time

Total

sample

time

PAGE 51

Methyl Bromide Specific Active Sampling Method (MBS–ASM)

Pump Information

Sample

Number

Make Model Equipment

type

Equipment

ID

Mode Notes

Sample Train Calibration

Sample

number

(as

above)

Equipment

ID

Flow Check

Equipment

ID

Start Flow

Rate l/m

End

Flow

Rate l/m

Difference

l/m

% Error

From

Start

Flow

Rate

Pass/Fail

PAGE 52

Sample location information – mark each sample location on plan sketch with and

associated sample number

Sample

Number

(as

above)

Location/

Name

Equipment

type and ID

Wind speed and

direction at sample

installation (m/s)

Distance from

centre of

fumigated goods

(metres)

Notes

Pass/Fail Criteria TO-17 Only

If the % error between the start and end flow rate is less than 10% the test has passed the QA

criteria and the test is accepted. If the difference is greater than 10% the test fails the QA criteria

and the test is rejected.

If the test Passes and is accepted, calculate sample volume by multiplying the sample time by the

start flow rate. The sample volume will be used to determine the ambient air concentration over the

sample period.

PAGE 53

MeBr Gas Detection Tube Field Sheet

Sample # Location Type of Tube

(Manfacturer/

Range)

Date and

Time

Sampled

Result

(ppm)

Notes

PAGE 54

PAGE 55

Appendix B Case Study: Monitoring Method

PAGE 56

The following appendix sets out a step by step example of a complex ambient air monitoring event

of a methyl bromide fumigation venting carried out in New Zealand.

Background

The scale of the fumigation included fumigation release from ship holds and from log stacks

located in a secured port with surrounding complex terrain. The total amount of methyl bromide

used for the fumigation included 2502 kg within 5 ship holds and 377 kg within four log stacks

fumigated under covers.

Step 1 Site Assessment

The topography of the fumigation sites were assessed by aerial photography, topographical maps,

site photos and from a site walk around. The walk around also accessed the surrounding activities,

buildings and vegetation. The proposed location for the fumigation release was discussed with the

port operator. Local wind patterns were discussed with the port, historic metrological data was

interrogated and weather forecasts were reviewed and recorded on the monitoring filed sheets. The

weather forecast indicated that meteorological conditions would not result in poor dispersion

conditions although light winds would result in less than ideal dispersion conditions. If conditions

were likely to indicate very poor dispersion conditions the fumigation venting would be slowed and

may need to occur over two nights.

Step 2 Monitoring Location Selection

The selection of monitoring locations was based on the planned size and location of the fumigation

and on the site assessment discussed above. Because the planned fumigation was large, the local

topography made wind directions unpredictable and the forecasts winds were light and variable.

Six locations were selected for monitoring. The locations included three boundary points (outside

of the buffer zone) with public access (sensitive locations) that would be potentially downwind,

one location on the nearest downwind land sea boundary (within the 100 metre buffer zone), one

location upwind in the event the wind direction changed, and one location at the boundary location

crosswind. The site had a secure boundary much larger than the minimum 100 metre buffer zone

and the port authority established and monitored an exclusion zone over the water near the vessel

under fumigation. All sampling locations met the requirements set out in the GPG.

Step 3 Equipment Selection

PIDs were selected as the monitoring equipment based on the number of monitoring locations and

the need to provide fumigation venting control if required. While there was a small potential for

some VOC contamination from a local boat building facility the forecast winds did not indicate it

would become an upwind source. A total of nine PIDs were hired from multiple equipment

PAGE 57

suppliers for delivery two days prior to the fumigation release. A new charcoal filter, 15 GASTEC

methyl bromide detector tubes and a cylinder containing 100 ppm Isobutylene calibration gas were

purchased for the event. On receipt the samplers were removed from their cases and checked to

ensure they were operational.

Step 4 Monitoring Preparation

a) All monitors were powered up one day prior to the fumigation and the battery levels were

checked. Extra batteries were included with the units and could be needed based on the size

of the fumigation and expected slow venting required. The PIDs were also checked to

make sure that multiple moisture/dust filters were included.

b) The clocks of all the PIDs were synchronised and the instruments were set to log

automatically, historic data was cleared and the settings were changed to account for the

methyl bromide correction factor.

c) The calibration documents were collected and stored.

Step 5 Monitor Pre-monitoring Calibrations

A clean preparation area was established at the fumigation location. A full calibration for each

instrument was not carried out as the suppliers performed calibrations prior to dispatch. Zero and

span calibration checks were performed on all PIDs to ensure the calibration was still valid. Zero

calibrations were performed with charcoal filter at the PID inlets, and span calibrations were

performed using 100 ppm isobutylene gas. Full calibrations were performed on those monitors that

were not within +/-10% of the span and zero checks (span check readings within 10% of 170 ppm

were accepted to account for the methyl bromide calibration factor of 1.7). Calibrations were

carried out with PID pre-filters in line.

Step 6 Setup

a) Four hours prior to the fumigation venting the local weather conditions were recorded and

the selected monitoring locations were re-assessed. The weather conditions were similar to

the forecasted conditions used in the initial location selection so no changes were made to

the monitoring locations.

b) A meeting with the fumigators confirmed the schedule for the fumigation and to discuss

the monitoring schedule. The amount of methyl bromide used, amount of product or area

being fumigated was collected for the fumigation and recorded.

c) The Port was asked to confirm that the meteorological station was operating normally.

PAGE 58

d) One hour prior to the fumigation the local weather conditions were again recorded, and

remained similar to the last reports.

e) Information for each PID including make model and serial number were recorded in the

monitoring field sheet. Each PID was assigned to a location and this information was

recorded in the field sheet.

Step 7 Monitoring

a) Due to the large number of monitoring locations and the large monitoring area a second

technician was used to help perform checks on the monitoring locations.

b) PIDs were installed at the pre-determined monitoring locations 15 minutes prior to the

beginning of the fumigation release. Start times at each monitoring location were

recorded, PIDs were switched on and monitoring initiated prior to the fumigant venting.

Meteorological conditions were recorded both prior to and during the release event. All

PIDs were placed 1.5 metres above local ground level.

c) Observations were recorded during the fumigation venting and included fumigation

venting start times (per hold and per log stack), fumigation venting activities, local events

(i.e. large ships entering or exiting nearby, trucks or forklift movements near monitoring

locations etc), weather changes and anything else that could influence the monitoring

results.

d) During the fumigation venting the monitoring locations were checked every 15 to 30

minutes. The following checks and/or data were recorded during each pass: battery life,

logging status, current reading, peak reading, and location-specific wind data. Peak

readings were cleared following each walk around. PID pre-filters were changed half way

through the fumigation release to reduce the chance for moisture accumulation.

e) When a PID displayed a sustained readings above 0.5 ppmv a GASTEC methyl bromide

gas detection tube was sampled near the PID inlet to determine if the reading was methyl

bromide. If the reading was not confirmed to be MeBr by the GASTEC tubes, a charcoal

filter was applied to the PID inlet for a short period (5 to 10 seconds) to determine

whether the readings were due to instrument drift or non-target VOC interference.

NOTE: When a charcoal tube is applied to the PID inlet the PID is effectively sampling

air free of VOCS and the readings should drop to 0 ppmv. If they do not drop to 0 ppmv

then the instrument has drifted and should be replaced.

A second PID was also brought to the location to confirm instrument drift, and a backup

PID was used to replace the malfunctioning unit.

f) Monitoring was continued for a minimum period of 15 minutes after the instrument

readings dropped below 0.05 ppm, following the end of fumigation ventilation.

PAGE 59

g) At the end of monitoring all PIDs were switched off, the times and local weather

conditions noted, and the PID were returned to the prep area.

Step 8 Post monitoring checks and downloading

Following the end of monitoring each PID had a post monitoring calibration check. This involves

applying a zero air or carbon filter and recording the zero reading. A gas (100ppm Isobutylene)

was then introduced to the inlet of the PID as a span check. The values were then recorded on the

monitoring spread sheet. The data was then downloaded from each PID, including those that

malfunctioned.

Step 9 Data Processing

Following data download from the PIDs, data was exported into an Excel Format. Data is

generally recorded as one minute averages which were then converted to 1-hour and 24-hour

rolling averages. If an instrument was removed due to drift the data files from the original and

replacement monitor were combined to form a single file for the duration of the monitoring event.

Data was then presented as maximum 1-hour and 24-hour rolling averages for each location.

Step 10 Report Preparation

A report was then prepared including discussions on the fumigation operations, meteorology,

overall observation, a description of the reasoning and process for selection of the sampling

locations, data recorded and averaged during the monitoring event, interpretation of the data and a

conclusion.